Activity of neuronal populations of human subcortical structures during sleep

Multi-unit activity of 14 subcortical structures was studied during drowsiness and sleep in patients with depth electrodes implanted in the brain for therapeutic purposes. The mean firing rate of the multi-unit activity was found to decrease during "slow-wave" sleep in each cycle. The multi-unit activity was sharply increased during paradoxical sleep. In successive sleep cycles the mean firing rate somewhat increased from cycle to cycle during slow sleep. The mean firing rate was considerably increased during wakefulness after a sufficiently logn sleep, as compared with the initial background values. Fluctuations of the mean firing rate were characteristic of paradoxical sleep. When studying simultaneously 2 or 3 structures, both uniform or different changes of the neuronal activity were possible. Changes of the firing rate in separate structures may develop a few seconds prior to the "clinical display" of the REM phase. All (or nearly all) the structures, whose activity during sleep is rather independent, are presumed to be able to be a source of the REM phase.